Method of making flexible reinforced conduit



27, 1966 E. M. ROTHERMEL ETAL 3,294,607

METHOD OF MAKING FLEXIBLE REINFORCED CONDUIT Original Filed March 30,1959 2 Sheets-Sheet l FIG 1 FIG3 F G 4 VINVENTORS EDWARD M. ROTHERMELRUSSELL B. WADDELL, JR

Mama

ATTORNEY Dec. 27, 1966 E. M. ROTHERMEL ETAL 3,294,607

METHOD OF MAKING FLEXIBLE REINFORCED CONDUIT 2 Sheets-Sheet 2 OriginalFiled March 30. 1959 FIG-9 FIG-8 INVENTORS EDWARD M. ROTHERMEL JSSELL B.WADDELL, JR

M awe/M ATTORNEY United States Patent 3,294,607 METHQD OF MAKINGFLEXIBLE REINFORCED CONDUIT Edward M. Rothermel and Russell B. Waddell,Jr., Waynesville, N.C., assignors to Dayco Corporation, a corporation ofGhio Original application Mar. 30, 1959, Ser. No. 802,828, now PatentNo. 3,152,618, dated Oct. 13, 1964. Divided and this application July15, 1963, Ser. No. 298,516 6 Claims. (Cl. 156-144) This application is adivision of US. application Serial No. 802,828, filed Mar-oh 30, 1959,now Patent No. 3,152,618, issued October 13, 1964.

The present invention relates to reinforced flexible conduit andparticularly to such conduit which is fluid impervious and especiallyadapted for the transportation of fluid materials, particularly of agaseous nature. The invention relates further to an improved method forthe manufacture of such conduit.

Conduit of the general type referred to has been formed of a flexibletubular body portion composed of elastomeric or thermoplastic materialcircumferentially reinforced by means of axially spaced reinforcingturns provided by bonding to or embedding in the tubular body, a steelSpring member the coils or which may themselves have been first coatedwith elastomeric or thermoplastic material. Such conduits are describedand claimed in US. Patents 2,766,806, 2,782,803, and 2,822,857 andothers. Conduit of this type has been found to be light in weight,durable and flexible and has found application in connection withhousehold and industrial vacuum cleaners oxygen systems particularly forsupplying oxygen to aircraft crew members, respiratory devices, gas andliquid fuel supply systems and the like.

Conduit of the type described in the prior art has generally been formedby surrounding the reinforcing member with the tubular body and bondingit thereto or by embedding such reinforcing member wholly or partiallyWithin the tubular body. Products of this type have usually resulted inconduit in which the reinforcing member is exposed within the innersurface of the tube or in cases where complete embedment has resulted,the product has required a substantial thickness or has resulted inproducts which do not possess the maximum degree of flexibility whichmay be required.

It is accordingly an object of the present invention to provide a fluidimpervious conduit which is at once extremely flexible and which isreinforced against radial compression and collapse.

It is a further object of the present invention to provide a fluidimpervious conduit having a corrugated exterior surface and'in which thetubular body is positioned within and bonded to the inner surface of thereinforcing mernber.

It is a still further object of the present invention to provide aconduit in which the tubular body member is bonded to the inner surfaceof the reinforcing member and in which an outer tubular body ispositioned over the reinforcing member in a manner which will providesubstantial strength without substantially affecting the flexibility ofthe hose.

It is a still further object of the present invention to providereinforced corrugated conduit in which the reinforcing member surroundsand is bonded to an inner tubular layer and wherein an outer tubularlayer of the same or different composition surrounds the reinforcingmember and engages it without being bonded thereto.

It is a still further object of the present invention to provide amethod for the manufacture of a hose of the type described which will besimple, eflicient and of low cost.

Further objects will appear from a consideration of the specificationand drawing as described below.

It is seen that the present invention provides an improved conduitconstruction as well as a novel method for the manufacture thereof whichwill produce such conduit having improved flexibility and strength in asimple and effective manner and which permits considerable variation instructure and composition. These results are achieved by forming areinforcing member of spaced convolutions of predetermined diameter inthe form of a spring or spaced annular turns or the like, saidconvolutions being preferably first coated with a layer of elastomericor thermoplastic material, forming a tubular member of elastomeric orthermoplastic material of a predetermined diameter less than thediameter of the reinforcing member, expanding the tubular member withinits elastic limits so that it engages the inner surface of thereinforcing member and becomes bonded thereto, and thereafter allowingthe inner tubular member to resume its normal diameter. The resultantprod uct is one in which the tubular body is bonded to the reinforcingmember which surrounds it along the inner periphery of said reinforcingmember with the result that the bonded areas of the tube are restrainedwhile the unbonded areas between convolutions of the reinforcing memberare depressed due to the tendency of the tube to resume its normaldiameter. A corrugated product is thereby formed in which thecorrugations of the tube are in tension. The resulting product ispreferably strengthened and reinforced by positioning an outer tubularlayer of resilient material over the reinforcing member in such a mannerthat the second tubular layer is also formed to have a diameter lessthan that of the reinforcement and is expanded and positioned over thereinforcemnt after which it is allowed to relax and embrace theconvolutions of the reinforcement so that it too will have a corrugatedconfiguration.

The material of which the tubular body is formed may be selected fromthe resilient somewhat elastic materials represented by natural orsynthetic rubber and certain plastic materials also having resiliencyand elasticity. These plastic materials are generally of thermoplasticnature, such as polyvinyl chloride, polyethylene and the like. Whenvulcanizable material, such as natural or synthetic rubber is used, itis utilized in the partly vulcanized or vulcanized state since it willpossess the required degree or inherent elasticity in such condition.The reinforcements may be of steel, aluminum, or other metal, or may beof rigid plastic such as nylon, polystyrene, etc.

The above described principles and advantages of the present inventionmay be more clearly understood by the following description inconnection with the accompanying drawing in which,

FIG. 1 is a view partly in cross section and partly in elevationillustrating one step in manufacture of the product of the invention.

FIG. 2 is a view partly in elevation and partly in cross sectionillustrating a later step in the manufacture of the invention.

FIG. 3 is a view partly in elevation and partly in cross sectionillustrating the product resulting from the steps illustrated in FIGS. 1and 2.

FIG. 4 is an enlarged cross-sectional view of a portion of the hose ofFIG. 3.

FIG. 5 is a view partly in cross section and partly in elevationillustrating a final step in the manufacture of another product of theinvention.

FIG. 6 is a view in elevation and partly in cross section illustratingthe structure of the product made in accordance with the steps of FIG.5.

FIG. 7 is a view partly in elevation and partly in cross section showingthe product of FIG. 6 in an axially elon-" gated condition.

FIG. 8 is an enlarged cross-sectional view of a portion of the hose ofFIG. 7.

FIG. 9 is a view similar to FIG. 8 illustrating a modified form of theinvention.

As shown in FIG. 1, mandrel 10 is provided with an expansible elasticcovering member 11, commonly known as an air bag, which is formed ofelastic or stretchable material such as vulcanized rubber or the like.The mandrel and air bag are of such dimensions that the air 'bag fitssnugly over the mandrel and the diameter of the air bag is slightly lessthan the diameter of elastomeric tube 12 which is drawn thereover. Tube12, which may be formed by extrusion, is of elastomeric materialreferred to above and is formed of a diameter which represents thenormal inner diameter of the conduit to be produced and which isnormally smaller than the inner diameter of the reinforcing members asdescribed further below. Preferred materials for the tube 12 are elasticthermoplastic materials such'as polyvinyl chloride or polyethylene, orvulcanized or partially vulcanized natural or synthetic rubber, in orderthat the tube may be stretched and thereafter relaxed to normaldiameter. After tube 12 is placed over the air bag on the mandrel,reinforcement 13 in the form of spaced convolutions of a steel spring,is positioned over the tube as shown. The convolutions are formed with adiameter which will conform to the desired outer diameter of the conduitplus any outer tube or layer applied thereto, and also the convolutionsof the spring are also preferably coated with a layer 14 of elastomericmaterial which may be of the same type as the tube but not necessarilyso. Mandrel 10 is provided with an inner bore 15 and radial passages 16extending between the bore and the surface of the mandrel. Asillustrated in FIGURE 2, upon the introduction of air or other fluidunder pressure internally of the mandrel the fluid causes air bag 11 toexpand and stretch carrying with it tube 12. The expansion is carriedout sufliciently to cause tube 12 to press against the inner peripheryof the reinforcing turns of member 13 and against coating 14 thereon.This enables the tube to become bonded to the inner surfaces of thereinforcement. In order to properly effectuate this bond, the tube maybe first coated with a suitable adhesive and the internal pressure isretained until the adhesive becomes set. In lieu of using an adhesive,and particularly where the tube and the coating on the reinforcement areof a thermoplastic nature, heat maybe applied preferably in a localizedmanner by conducting electric current through the wire of thereinforcement, which causes softening of the tube and the coating on thewire at their points of contact. Upon discontinuance of the electriccurrent and cooling of the wire the thermoplastic material becomes setand an integral bond takes place between the tube and the coating on thewire. If desired, the entire assembly may be introduced into a heatingzone of an induction furnace and the wire may be heated and thelocalized heating of the wire may take place by induction. Where thetube and the coating on the wire are of partially vulcanized rubber,bonding may be effected by introducing steam or hot air into the air bagwith the resultant heat enabling the tube and the coating on the wire tobecome completely vulcanized while in pressure engagement with eachother. In case both tube and coating on the wire are of vulcanizedrubber a bond may be obtained by the use of an adhesive such as a rubberor resin cement or a rubber solvent applied to the wire or to the tubeor both before contacting them. Once the bond has been effected, theinternal pressure upon the air bag is released and the resultantassembly removed.

As shown in FIG. 3 the assembly consists of a tube 12 to whichreinforcement turns 13 are bonded along the outer surface of the tubeand at the inner periphery of the reinforcement as shown. In view of theinherently elastic nature of the material of the tube it tends to returnto its original diameter which is less than the diameter of thereinforcement with the result that corrugations or convolutions areformed depending between the reinforcement turns as shown. The resultantproduct may in many cases by utilized in this form in case a single tubehaving a light weight construction is desired. This would beparticularly true in cases where the conduit is to be utilized withfluid having a low positive or negative pressure since the stress uponthe bond between the reinforcement and the tube would not be especiallyhigh.

However, for most purposes additional reinforcement of the tubularmember is desired and in such cases a second tubular layer is appliedthereover in the manner illustrated in FIG. 5. As shown, the assembly ofFIG, 3 is positioned within an expansion chamber 18. This chamber isprovided with a fitting 19 which is provided with a passageway 20connected to a source of vacuum, such as a vacuum or exhaust pump.Within the tubular chamber 18 is positioned tube 21 the ends of whichare cuffed over the edge of the chamber in order to seal the spacebetween the tube and the inner wall of the chamber in order that thetube may be expanded by suction by being drawn inwardly against the wallof the chamber when suction is applied. The tube 21 is initially formedby extrusion or otherwise to have a diameter corresponding substantiallyto the initially formed outer diameter of tube 12 while the expansionchamber has a suitably greater inner diameter. As a result and asillustrated in FIG. 5, when the vacuum is released, tube 21 will tend toreturn to its original diameter and frictionally embrace thereinforcement 13 as well as tube 12 to form a second outer layersurrounding the reinforcement and the inner tube. The resulting productis then removed from the chamber and will possess the structureillustrated in FIG. 6. As shown in that figure, reinforcing member 13with its coating 14 is bonded to inner tube 12 which depends inwardunder tension between the coils of the reinforcing member. Outer tube 21surrounds and embraces the reinforcement and the inner tube undertension and conforms to the corrugations thereof but is unbondedthereto. This is further illustrated in FIG. 8.

As will be seen in FIG. 7 the resulting product may be freely elongatedaxially of the hose by stretching in which condition the interior willbe relatively nonobstructed and of increased diameter due to the factthat the depending convolutions of the tubes have become elongated asthe axial stress is applied. This results in the inner tube elongatedbetween convolutions and the outer tube also being elongated since itisin frictional engagement with the outer surface of the reinforcement andthe exposed surface of the inner tube. Some slippage of the outer tubewith respectto the inner assembly will occur when the conduit isstretched or bent.

A modified form of the invention is illustrated in FIG. 9 in which tube12 is provided to which reinforcing member 13 and its elastomericcovering 14 are bonded in a manner described above in connection withFIGS. 1 to 3. Prior to the application of the outer tube 21 a fabrictape 25 is applied over the convolutions of the reinforcement as shown,in order to provide additional reinforcement in this area. The tape maybe of a somewhat elastic and stretchable fabric so that it may beapplied under tension in which case bonding may be unnecessary. However,in general it is preferred to bond the tape over the convolutions of thespring by first applying adhesive thereto, such as a rubber cement. Theouter tube is then applied in the manner described in FIGS. 3, 5 and 6.This construction is desirable in cases where deep convolutions aredesired which would result in considerable degree of stress upon theelastomeric tubes but will provide a hose having a high degree ofstretch. These deep convolutions are obtained by forming the tubes to adiameter of substantially less than that of the reinforcement whichwould mean that during fabrication the tubes are stretched to a corre pnd ngly greater degree and upon relaxation will be drawn down betweenconvolutions of the reinforcement to a point considerably below theinner surfaces of the reinforcement to produce deep convolutions. At thesame time, this will tend to draw the convolutions together and shortenthe hose. On the other hand when the a hose is stretched, the degree ofstretch will be determined by the depth of the convolutions.

In view of the fact that the outer tube in this conduit need not bebonded, the conduit may be formed utilizing a pair of tubular memberswhich are not necessarily of the same composition and which wouldotherwise be incompatible by fusing or vulcanization or which would bediflicult to bond together. Thus the inner tube may be of rubber orpolyvinyl chloride and the outer tube of polyethylene, or vice versa.The outer tube may be of a material which is especially resistant tofactors to which the outer surface is exposed and may be of especiallywear or abrasion resistant material, or material which is resistant tosunlight and similar conditions. As one example of such a combination,the conduit may be formed of an inner layer of rubber or polyvinylchloride and an outer layer of butyl rubber, neoprene, orchlorosulfonated polyethylene.

We claim:

1. A method for the manufacture of flexible reinforced conduitcomprising the steps of forming a tube of elastomeric material having apredetermined diameter, positioning thereover a circumferentialreinforcing member having axially spaced coils with an inner diametergreater than the diameter of said tube, radially expanding said tubeWithin its elastic limits to cause portions of its outer surface toengage the inner surfaces of said coils, bonding the so engaged surfacesto each other and releasing said tube from its expanded position tocause said tube to depend inwardly between said coils.

2. A method according to claim 1 in which bonding is carried out byheating the contacting surfaces of the coils and the tube.

3. A method according to claim 2 in which said coils comprise metal andthe heating is carried out by the passage of electric current throughsaid coils.

4. A method according to claim 2 in which said coils comprise metal andthe heating is carried out by induction heating of said coils.

5. A method according to claim 1 in which bonding is carried out byapplying an adhesive between the contacting surfaces of the tube and thecoils.

6. A method according to claim 1 including the steps of preforming asecond tube of elastomeric material having a diameter less than theouter diameter of the reinforcing member, radially expanding said secondtube Within its elastic limit to a diameter greater than that of thereinforcing member, positioning the assembled first tube and reinforcingmember within said second tube while it is in the expanded state, andreleasing said second tube from its expanded state to cause portions ofsaid second tube to embrace said coils and to cause the other portionsthereof to depend inwardly between said coils.

References Cited by the Examiner UNITED STATES PATENTS 2,570,259 10/ lMcKinley 15 6143 2,743,759 5/1956 Snow et al 156143 2,822,857 2/ 1958Rothermel et a1 156144 2,941,571 6/1960 Rothermel 156-275 X 3,076,7372/1963 Roberts 138-422 X EARL M. BERGERT, Primary Examiner.

P. DIER, Assistant Examiner.

1. A METHOD FOR THE MANUFACTURE OF FLEXIBLE REINFORCED CONDUITCOMPRISING THE STEPS OF FROMIMG A TUBE OF ELASTOMERIC MATERIAL HAVING APREDETERMINED DIAMETER, POSITIONING THEREOVER A CIRCUMFERENTIALREINFORCING MEMBER HAVING AXIALLY SPACED COILS WITH AN INNER DIAMETERGREATER THAN THE DIAMETER OF SAID TUBE, RADIALLY EXPANDING SAID TUBEWITHIN ITS ELASTIC LIMITS TO CAUSE PORTIONS OF ITS OUTER SURFACE TOENGAGE THE INNER SURFACES OF SAID COILS, BONDING THE SO ENGAGED SURFACESTO EACH OTHER AND RELEASING SAID TUBE FROM ITS EXPANDED POSITION TOCAUSE SAID TUBE TO DEPEND INWARDLY BETWEEN SAID COILS.